Grant: Operating Grant

Transforming growth factor-beta (TGF-B) is a hormone that is required for regulating blood cell production by controlling cell growth, death, and maturation. Inactivation of TGF-B regulated genes plays a key role in the development and abnormal growth of leukemia. Epigenetic silencing, due to modifications of DNA and histone proteins around which the DNA winds, is one mechanism cancers lose the ability to activate genes. p15 and p21 are TGF-B regulated genes that instruct cells to stop growing and are activated by TGF-B in normal cells but not in cancer cells. Recently, large RNA molecules, referred to as natural antisense transcripts (NATs), have been implicated in epigenetic silencing of p15 and p21. We showed that TGF-B fails to activate p15 and p21 but that the response to TGF-B can be regained in leukemia cells by treatment with so called epigenetic drugs that inhibit DNA methylation and modify histones. We now have preliminary data showing that by reducing the levels of p15 and p21 NATs in leukemia cells we can restore the responsiveness of p15 and p21 to TGF-B. The objective of this proposal is to characterize the role of NATs in keeping these critical growth suppressing genes in an unresponsive state. We will use genetic engineering techniques to deplete leukemia cells of p15 and p21 NATs and then characterize these effects on DNA methylation, histone modifications, gene activation, interaction with epigenetic drugs, responses to TGF-B, and leukemia cell growth. Understanding the role of NATs in epigenetic silencing of TGF-B regulated genes is essential for developing therapies to restore TGF-B responsiveness and thereby treat leukemias. This knowledge is vital for designing new treatment strategies to re-express individual genes silenced by epigenetic mechanisms in leukemias. As these disease mechanisms are likely to be fundamental to cancer cell biology, the insights gained from our study are likely to have broad applicability to other cancers.